Manufacture of musk xylene



Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE.

MANUFACTURE OF MUSK XYLENE Walter V. Wirth, Woodstown, N. J., assignorto E. I. du Pont de Nemours & Company, Wilmington, Del., a corporationof Delaware No Drawing.

Application February 1, 1934.

Serial No. 709,287

3 Claims.

NOa- N 0 2 Q:- CH;

which is known as musk xyelene.

Musk-xylene has heretofore been manufac-.

tured by nitrating tertiary-butyl-meta-xylene(1,3-dimethy1-S-tertiary-butyl-benzene) in a two- 7 step processinvolving the use of fuming nitric acid and 25% oleum in succession.(Ullmann, Enzyklopaedie der technischen Chemie, 1st edition, vol 9, page615.) This process not only involves theme of costly acids, but itsyield is relatively low, being in the order of in the process reported.This process has also the further disadvantage that it requires the useof costly, special-metal or enameled apparatus, due to the highconcentration of the reagents employed, and suifers in general from theinconvenience and hazard attendant upon the use of fuming acids. 7

It is accordingly an object of this invention to provide an improved andeconomical process for the nitration of tertiary-butyl-meta-xylene. Itis a further object of this inventionto provide a process for thenitration of tertiary-butyl-metaxylene, whereby the desired product,musk-xylene, is obtained in exceptionally high yield. Other and furtherimportant objects of this invention will appear as the descriptionproceeds.

I have found that tertiary-butyl-meta-xylene can be nitrated eflectivelyand efiiciently by the aid of mixed nitrating acid. Moreover, I havefound that when a mixture of nitric and sulfuric acids is used asopposed to the fuming nitric and fuming sulfuric acid of the previousart, the yield is considerably increased, approaching the theoretical.

My improved process accordingly consists of reacting upontertiary-butyl-meta-xylene with a mixed nitrating acid, that is amixture of nitric and sulfuric acids. The concentration of nitric acidin the mixture may vary within wide limits, for instance between 12 and50% by weight of the mixture. For practical reasons it is advan- Moreparticularly it relates tageous to use nitrating mixtures as occur incommerce.

I found that the ratio of nitric acid to that theoretically requiredwith a given quantity of tertiary-butyl-m-xylene need not be soexcessive a as indicated in the literature. In the process disclosed inUllmann, above cited, an excess of 83% of nitric. acid was employed. Inmy process satisfactory results are obtained with substantiallytheoretical quantities. Excesses, however lO do no harm, and the processmay be practiced in general with from 3 to '6 mols. of nitric per mol.of the hydrocarbon.

My improved process enables the reaction to-be carried out in standardcast iron apparatus. It 15 also eliminates the inconvenience and hazardof handling fuming nitric and sulfuric acids. Finally, in my process thehydrocarbon and nitrating mixture may be mixed in one step, as opposedto the successive addition of the two reagents in the process reportedby Ullmann. Without limiting my invention to any particular procedure,the following examples are given to illustrate my preferred mode ofoperation. Parts given are by weight. 7 5.

Example 1 A cast iron kettle, equipped with an agitator, heating andcooling jacket, etc., was charged with r 800 parts of a commercial-mixed acid, contain- 7 ing 70% H2SO4 and 30% HNOs .27 times theory ofnitric acid). 162 parts of tertiary-buty'l-me xylene (1 mol.) were addedgradually over a period of 1 hours, keeping the temperature of thenitration mass at 33 to 3 5 C. The mass was 35 then heated to 110 C.over a period of hour; and kept at 110-112 C. for 3 hours. At this pointthe crystalline reaction product became molten and remained'as an oiluntil cooling was applied. The mass was cooled gradually to C. V Vover'a period of 1 hour'to obtain well-formed Theproduct was purified bycrystallizing twice I from 1900 parts of alcohol; 261.4 parts' of puremusk xylene were obtained, melting at 113.4 55

The crude musk xylene crystals were fil- 45 I to 113.8 C., whichcorresponds to 88% of theory on the basis of the initial material.

Example 2 162 parts of tertiary-butyl-m-xylene were added gradually to730 parts of mixed acid (50% HNO3+50% H2804) over a period of 1 hours,keeping the temperature under 20 C. The mass was heated to C. over /2hour and held at 70 C. for 3 hours. It was cooled at 30 C. and worked upas in Example 1. 291 parts of crude musk xylene were obtained.

Example 3 162' parts of tertiary-butyl-m-xylene were added gradually to357 parts of mixed acid (50% I-INO3-l-50% H2304) over a period of 1hour, keeping the temperature at 25-30 C. The mass was stirred for 15minutes at 25-30 C. and then 324 parts of mixed acid (12.6% I-INO3-l-87%H2SO4) were added over a period of 20 minutes, keeping the nitrationmass at 25-30 C. Finally, 162 parts of the latter mixed acid were addedover 15 minutes, while allowing the temperature to rise to 40 C. Thenitration mass was stirred at 40 C. for 10 minutes and heated to C. overhour. It was cooled to 70 C. over A; hour and held at 70 C. for twohours. After that, it was cooled to 30 C., and worked up as inExample 1. 291 parts of crude musk xylene were obtained, or 98% oftheory.

It will be understood that the processes above set forth are susceptibleof variation within wide limits, as regards the amounts of mixed acidused, the percentage of nitric and sulfuric in the mixed acids, thetemperature of nitration and the time required to add the components. Itwill be further understood that the invention is not limited to the useof anhydrous mixed acid. Any of the hydrated commercial grades may beused; for instance, the grade consisting of or the grade 12:80:8; exceptthat a larger quantity of 'the nitrating agent will be required tooifset the weaker nitrating power of the acid due to dilution withwater.

It will also be understood that it is not necessary to crystallize thereaction product in the nitrator before drowning the nitration mass. Thehot nitration mass, in which the musk xylene is in the molten condition,may be added slowly to ice water to granulate the product. Furthermore,it will be understood that in case insuflicient mixed acid is used tocomplete the nitration in one step, more mixed acid of various strengthscan be added after the addition of the tertiary- 5 butyl-m-xylene and incase the original mixed acid is too weak in sulfuric acid to drive thereaction to completion, more sulfuric or'fuming sulfuric acid may beadded after the addition of the hydrocarbon. 10

The advantages of my improved process will now be readily apparent.

First, my process is carried out in one step, Where the art required theaddition of nitric and sulfuric acids in two separate steps. Second- 151y, I use the cheaper commercial mixed acid where the art called forexpensive fuming nitric and fuming sulfuric acids. Thirdly, the requiredexcess of nitric acid for efiicient working is much less in my processthan in the art (27% as com- 20 pared to 83%). Fourthly, the handling ofmixed. acid is considerably more convenient and .less hazardous than thehandling of fuming acids, and the apparatus required is of the standardcastiron type. Finally, the yield is much higher in 25 my process thanin that described in the literature. Moreover, the crude obtainable inmy process is of such excellent quality that it may be purified directlyfrom-alcohol, whereas the prior art found it necessary to purify firstfrom 3,0.

acid, containing between 12.6 and 50% by weight 45 of :nitric acid.

3. In the process of producing musk-xylene, the step which comprisesadding gradually tertiary-butyl-m-xylene to a commercial grade of mixednitric and sulfuric acid at a tempera- 50 ture of about 20 to 40 C., andthen raising the temperature to about '70 to 112 C., "to complete thereaction.

WALTER V. WIRTI-I.

